As far as I can tell from my research, there are only five of those symbols that are meant for use by general aviation pilots.
  • Require Assistance = V
  • Require Medical Assistance = X
  • Proceeding in This Direction = -->;
  • Affirmative = Y
  • Negative = N

The places that listed these five also stated, "if in doubt, use 'SOS'." It seems that all the other signals are for use outside the survivor's communication needs, such as SAR-to-SAR (ground-to-air) communications or military communications, etc.
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